1. Field of the Invention
The present invention relates to a reclining device, and specifically to a reclining device with an angular position memory mechanism which is optimally applied for a reclining seat back of a two-door type vehicle.
2. Description of the Prior Art
As is generally known, in two-door type vehicles with a front reclining seat, it is advantageous that an angular position memory for a reclining seat back is incorporated in the reclining device in consideration with easy getting in and out of a car. For instance, when the seated passenger on the rear seat gets out the car, the seat back of the front seat is inclined forwards by pulling the reclining seat lever. Thereafter, in the case the vehicle passenger sits on the front seat, the seat back of the front seat is backwardly inclined again. In this case, the angular position memory acts to retain the seat back at the preset angular position. Thus, the reclining seat with the angular position memory is free from troublesome setting of the seat back to the desired angular inclination. On earlier-model vehicles, a reclining device with an angular position memory mechanism for a seat back and a seat slide are both employed to ensure fore-aft angular inclination adjustment of the seat back and fore-aft position adjustment of the seat cushion. A reclining device with a reclining angular position memory mechanism has been disclosed in Japanese Patent Second Publication (Tokko Heisei) No. 4-25803.
The previously-noted conventional reclining device with an angular position memory is attached onto a base plate on which a seat cushion is mounted. The reclining device includes a sector gear (upper toothed plate) rotatably received on a main pivot shaft rotatably attached onto the base plate. The sector gear is firmly fixed to a seatback-side arm. The arm is firmly secured to the seat back by means of bolts and rotatably received by the main pivot shaft of the base plate. The reclining device also includes a pivotable lock plate (lower toothed plate) having a toothed portion which is brought into meshed contact with the sector gear to prevent rotational movement of the sector gear to the base plate of the seat cushion so that the seat back is held at a desired angular position. A reclining-seat operating lever is provided to cause pivotal movement of the lock plate. Additionally, the reclining device includes an angular position memory mechanism which will be hereinafter abbreviated as only a memory. The memory comprises a spring-loaded memory lever which has a toothed portion and is pivotally supported by way of a pin mounted on the sector gear or the arm, and a main memory plate having a sectoral toothed portion which is meshed with the toothed portion of the memory lever through pivotal movement of the memory plate when the memory lever is held unloaded. The main memory plate is rotatably supported by the main pivot shaft. The memory includes a pair of auxiliary memory plates both associated with the main memory plate in such a manner as to sandwich the main memory plate. These auxiliary memory plates cooperatively function to hold the main memory plate in the preset angular position, when reaching the preset angular position. The memory also includes a sector-gear side sliding-contact member which is responsive to a forward inclining movement of the seatback arm to cause a smooth sliding-contact surface formed on the outer periphery of the contact member to be put into contact with the toothed portion of the lock plate in the event of the forward angular inclination of the seat back.
During angular inclination adjustment, the seated passenger on the front seat displaces an angular position of the seat back to a desired position and then the memory lever is engaged with the main memory plate to mechanically memorize the desired angular inclination. In the prior-art reclining device disclosed in the Japanese Patent Second Publication No. 4-25803, if the seat back is inclined forwards by the operating lever in order that the seated passenger on the rear seat gets out of the car, the outer peripheral toothed portion of the lock plate does not mesh with the sector gear but with the sector-gear side sliding contact member. Under this condition, in the event that the seat back is rotated in the backward angular inclination direction, the sliding contact member is disengaged from the outer peripheral toothed portion of the lock plate since the sector-gear side sliding-contact member is pushed and rotated by the main memory plate when the seat back or the main memory plate reaches the preset angular inclination. As a result, the lock plate meshes with the sector gear, thereby ensuring the recovery of the seat back to the memorized reclining angular position. The previously-noted conventional reclining device with an angular position memory includes a sliding-contact member engageable with a lower toothed lock plate to prevent direct contact between toothed portions of an upper sector gear and a lower lock plate during forward inclining motion of the seat back, particularly at most forward inclination position of the seat back and consequently to avoid tooth wear. However, there is a possibility that undesirable tooth wear still occurs owing to sliding contact between the sliding-contact member and the toothed portion of the lock plate. To avoid sliding contact between the toothed lock plate and the sector-gear side sliding-contact member, Japanese Patent Second Publication (Tokko Heisei) No. 4-25804 teaches the provision of an additional sliding-contact member attached onto the lock plate. At a forward angular inclination position of the seat back, the two sliding-contact members cooperate in sliding contact relation with one another, thereby preventing tooth wear of the toothed portion of the lock plate owing to forward inclination movement of the seat back. With the above-noted arrangement of the reclining device disclosed in the Japanese Patent Second Publication No. 4-25804, there is a great frictional force between the two sliding-contact members at the forward inclination position. Traditionally, the seat back is biased forwards by virtue of a spiral spring or a power spring. In the event that the vehicle passenger shifts the seat back from the forward inclination position to the backward inclination position, the backward inclining effort of the passenger becomes thus increased owing to the sum of pre-load applied to the spring-loaded seat back and the frictional force between the two sliding-contact members.